Process of producing duplicate sound bands



STATES PATENT OFFICE PROCESS OF PRODUCING DUPLICATE SOUND BANDS Hugo Westerkamp, Cologne-Poll, Germany; vested in the Alien Property Custodian No Drawing. Application January 6, 1941, Serial No. 373,378. In Germany December 13, 1939 2 Claims.

The invention relates to a method of producing duplicate sound bands in quantity with mechanical sound record.

For producing such sound hands it has been proposed to use a matrix made from an original sound band for pressing a thermoplastic band with the application of heat and pressure. In this hot pressing, especially, the accomplishing of the pressure to be applied causes considerable difficulties with those thermoplastic substances which enable the most perfect forming with the matrix, as for example with cellulose derivates or certain artificial resins, particularly with substances having a polyvinylchloride base, since these are most diflicult to form and require a very high pressure.

Apart from the hot pressing method, cold pressing methods have become known which, however, still cause much greater difficulties in forming with the matrix so that it became necessary to resort to bands consisting of comparatively easily mouldable substances. In order to be able to use bands consisting of harder materials, it has been proposed to subject the bands to a preliminary softening treatment with swelling or dissolving agents. However, this is connected with difficulties in the subsequent removal of the swelling or dissolving agents. Even by placing the ready pressed bands in heating chambers, it was not possible to completely remove the solvent. Moreover, the application of swelling and dissolving agents leads to a softening of the sound band material which easily results in undesired expansions or contractions of the sound band.

The object of the present invention is to obviate these disadvantages. This is achieved by pressing the matrix on a thermoplastic band treated with a dissolving or swelling agent under simultaneous application of heat, the pressure being applied to the treated band before subjecting it to the heat, and the pressure being maintained after the actual moulding is finished. The starting of the pressure before heat is applied and the continuing of the pressure after the actual moulding operation is finished serves to prevent expansions and contractions of the sound band and, therefore, distortions of the sound record, whereas, at the same time, the close contact between the treated thermoplastic band and the hot matrix results in a practically complete removal of the swelling or dissolving agent.

Preferably, the sound band is cooled after having been pressed under simultaneous application of heat and pressure, the pressure being kept up until the sound band has cooled down.

A further feature of the invention consists in the fact that the pressure between the sound band and the matrix is gradually increased until a maximum is reached, at which the heat is applied to the sound band, and is then gradually reduced again.

According to an example of the invention, an unrecorded or blank sound band consisting of a cellulose derivative is subjected to a swelling operation by spraying amyl acetate thereon. Thereupon, the band is brought into contact with the matrix produced from the original sound record. The band and the matrix are then pressed together with slight pressure, this pressure being gradually increased to the actual moulding pressure, at which the heat is applied. After the moulding operation is finished, the sound band and the matrix are kept under pressure for some time without further application of heat, whereupon the matrix and the band are cooled. During this cooling, the pressure between the matrix and the sound band is continued, though to a reduced extent. When the matrix and the sound band have cooled down, the matrix is detached from the sound band which now is in a perfectly pressed state.

The invention may be applied to interrupted as well as to progressive pressing methods.

What is claimed is:

1. The process of producing duplicate sound bands in quantity, having mechanical sound records thereon, by employment of a matrix prepared from an original sound band and having thereon the record to be reproduced, which comprises treating a thermoplastic blank band with a volatilizable softening agent, pressing the matrix upon the softened blank band, subjecting the band to heat while continuing the pressure of the matrix for effecting the elimination of the softening agent, cooling the impressed band while continuing the pressure of the matrix thereon whereby to prevent deformation during the cooling, and detaching the matrix from the sound band.

2. The method of producing duplicate sound bands in quantity, having mechanical sound records thereon, by employment of a matrix prepared from an original sound band and having thereon the record to be reproduced, which comprises treating a thermoplastic blank band with a volatilizable softening agent, pressing the matrix upon the softened blank band with a pressure which gradually increases to a maximum, subjecting the band to heat after said pressure reaches a substantial maximum and continuing the pressure and heating for effecting the elimination of the softening agent, gradually reducing the pressure and permitting the band to cool, a pressure being maintained upon the sound band until it has entirely cooled whereby to prevent deformation during the cooling, and detaching the matrix from the sound band.

HUGO WESTERKAMP. 

